In capturing a scene with a camera, many parameters affect the quality and usefulness of the captured image. In addition to controlling overall exposure, exposure time affects motion blur, f/number affects depth of field, and so forth. In many cameras, all or some of these parameters can be controlled and are conveniently referred to as camera settings.
Methods for controlling exposure and focus are well known in both film-based and electronic cameras. However, the level of intelligence in these systems is limited by resource and time constraints in the camera. In many cases, knowing the type of scene being captured can lead easily to improved selection of capture parameters. For example, knowing a scene is a portrait allows the camera to select a wider aperture, to minimize depth of field. Knowing a scene is a sports/action scene allows the camera to automatically limit exposure time to control motion blur and adjust gain (exposure index) and aperture accordingly. Because this knowledge is useful in guiding simple exposure control systems, many film, video, and digital still cameras include a number of scene modes that can be selected by the user. These scene modes are essentially collections of parameter settings, which direct the camera to optimize parameters given the user's selection of scene type.
The use of scene modes is limited in several ways. One limitation is that the user must select a scene mode for it to be effective, which is often inconvenient, even if the user understands the utility and usage of the scene modes.
A second limitation is that scene modes tend to oversimplify the possible kinds of scenes being captured. For example, a common scene mode is “portrait”, optimized for capturing images of people. Another common scene mode is “snow”, optimized to capture a subject against a background of snow, with different parameters. If a user wishes to capture a portrait against a snowy background, they must choose either portrait or snow, but they cannot combine aspects of each. Many other combinations exist, and creating scene modes for the varying combinations is cumbersome at best.
In another example, a backlit scene can be very much like a scene with a snowy background, in that subject matter is surrounded by background with a higher brightness. Few users are likely to understand the concept of a backlit scene and realize it has crucial similarity to a “snow” scene. A camera developer wishing to help users with backlit scenes will probably have to add a scene mode for backlit scenes, even though it may be identical to the snow scene mode.
Both of these scenarios illustrate the problems of describing photographic scenes in way accessible to a casual user. The number of scene modes required expands greatly and becomes difficult to navigate. The proliferation of scene modes ends up exacerbating the problem that many users find scene modes excessively complex.
Attempts to automate the selection of a scene mode have been made. For example, United States Published Patent Application US 2003/0007076 A1, “Image Processing Apparatus and Image-Quality Control Method,” Noriyuki Okisu et al, assigned to Minolta Co., Ltd., published Jan. 9, 2003, teaches a method for automatic selection of scene mode based on focus data, scene brightness, and focal length. Similarly, U.S. Pat. No. 6,301,440, “System and Method for Automatically Setting Image Acquisition Parameters,” Rudolf M. Bolle et al, assigned to International Business Machines Corp., issued Oct. 9, 2001, teaches a method for automatic selection of a scene mode and use of a photographic expert unit to automatically set parameters for image capture. Both of these methods disclose ways to use information from evaluation images and other data to determine a scene mode. The scene mode then is used to select a set of capture parameters from several sets of capture parameters that are optimized for each scene mode.
A limitation on automated methods is that such methods tend to be computationally intensive relative to the simpler methods. Cameras tend to be relatively limited in computing resources, in order to reduce cost, cut energy drain, and the like. This has resulted in noticeable lag between shutter trip and image capture in some cameras. Such lag is highly undesirable when a subject to be photographed is in motion. One solution to the problem of lag is avoidance of highly time consuming computations. This leads back again to the use of modes.
It would thus be desirable to provide improved cameras and methods, in which camera settings are automatically determined and the above shortcomings are at least partially mitigated.